Hydrocarbon conversion catalyst



Unite US. Cl. 252451 6 Ciaims ABSTRACT OF THE DISCLOSURE A catalystmanufacturing process. The catalyst is a faujasite dispersed in anamorphous silica matrix. The catalyst is manufactured by adding thefaujasite together with the mother liquor from which it was precipitatedto a silica sol and then effecting gelation.

Background of the invention For many years heavy petroleum hydrocarbonfeed stocks boiling in excess of about 400 F. have been converted tolower boiling hydrocarbons in the motor fuel boiling range by heatingthem at a temperature in the 600 F.ll F. range in contact with anamorphous silica-alumina catalyst. While other silica composites e.g.,silica-zirconia, silica-magnesia, etc. have been known to catalyze thecracking reaction, the silica-alumina composite has been by far the mostwidely accepted catalyst in the industry. More recently, improvedcatalysts have been prepared by the inclusion of certain finely dividedcrystalline alumino-silicates, particularly the synthetically preparedfaujasites, within the amorphous silica-alumina matrix.

While an amorphous silica has never been considered to be competitivewith an amorphous silica-alumina composite as a cracking catalyst, ithas been observed that the inclusion of a faujasite in the silica matrixresults in a catalyst comparable to or better than one whereby thefaujasite is included in an amorphous silica-alumina matrix. This offersa number of advantages, not the least of which is the considerablereduction in the cost of catalyst manufacture.

The art discloses a number of methods applicable to the preparation ofthe catalyst herein contemplated, all of which require the recovery ofthe faujasite as a finished product prior to distribution thereof in asiliceous matrix. For example, it is the common practice to prepare thefaujasite by the method whereby an appropriae mixture of oxides, or ofmaterials whose composition can be completely represented os a mixtureof the oxides SiO Alpog, Na O and H 0, is heated together in an aqueoussolution with the formation of a faujasite. Preliminary to dispersingthe faujasite in the siliceous matrix by prior art methods, it isconsidered essential that the faujasite be first separated from itsmother liquor and water-washed until the water in equilibrium with theproduct is free of soluble salts and amorphous silica. Usually an alkalimetal aluminate is used as a source of alumina and, together with analkali metal hydroxide, as a source of alkali metal ions. The nature ofthe reaction requires that considerable excess of silica be employed,the excess being subsequently recovered in the mother liquor anddiscarded.

It is then an object of this invention to present a novel process forthe manufacture of a catalytic composite comprising a faujasitedispersed in an amorphous silica matrix. It is a further object topresent a novel method of dispersing a faujasite in an amorphous silicamatrix whereby the faujasite is employed admixed with its mother liquor.It is still another object to utilize the mother liquor as a source ofamorphous silica.

ttes Patent 0 Summary of the invention In one of its broad aspects, thisinvention embodies a process for the manufacture of a catalyticcomposite comprising a faujasite dispersed in an amorphous silicamatrix, which process comprises (a) preparing a faujasite dispersed inits mother liquor, (b) rapidly dispersing the faujasite-mother liquormixture in an acidified alkali metal silicate solution having a pH inexcess of about 2.5, controlling the pH during the faujasite-motherliquor addition so as not to exceed about 4.5, the final pH of themixture being from about 4.0 to about 4.5, and effecting gelation of themixture (c) adjusting the pH of the resulting slurry to a pH of fromabout 5 to about 8 and aging the slurry for at least about 0.5 hour, (d)separating the resulting product and base-exchanging the same in contactwith a solution containing an ion capable of replacing alkali metal ionsand characterized by a pH in excess of about 4.5, (e) washing thebase-exchanged product free of soluble matter and drying the resultantcatalyst composite.

Other objects and embodiments of this invention will become apparent inthe following detailed specification.

Pursuant to the process of this invention a faujasite is prepared andutilized in its mother liquor. The faujasitemother liquor mixture hereincontemplated may be prepared in any conventional or otherwise convenientmanner. One preferred method comprises forming an aqueous solution of analkali metal aluminate and analkali metal hydroxide and adding saidsolution to an aqueous silica slurry. The alkali metal hydroxide isusually sodium hydroxide, and the alkali metal aluminate is usuallysodium aluminate, a sodium aluminate comprising a N21 O/AI O molar ratioof about 1.2 being suitably employed. The resulting reaction mixturepreferably comprises a Na O/SiO molar ratio of at least about 0.3 andgenerally not in excess of about 0.7, and a SiO /Al O molar ratio offrom about 6 to 20, suflicient to yield a faujasite productcharacterized by a SiO /Al O molar ratio of at least about 3.Preferably, the reaction mixture has a composition expressed in terms ofoxide mole ratios as follows:

SiO /Al O from 6 to 20 Na O/SiO from 0.3 to 0.7

H O/Na O from 25 to 60 In any case, faujasite is precipitated from thereaction mixture at a temperature of from about F. to about 245 F.utilizing a closed vessel to avoid the loss of water. It is preferred toage the reaction mixture for from about 1 to about 24 hours or more at atemperature up to about F. prior to heating at a highertemperatureusually about 212 F. By so doing, the desired faujasiteproduct is obtained substantially free of other zeolitic material. Afterthe preferred cold age, the reaction mixture is heated as aforesaid toeffect substantially complete precipitation of the faujasite productfrom its mother liquor.

The faujasite-mother liquor mixture is thereafter cooled and added tothe acidic sodium silicate solution in an amount to insure a finalcatalyst composite comprising from about 1.0 to about 60 weight percentfaujasite dispersed in a silica matrix, preferably from about 1.0 toabout 10 weight percent. The faujasite dispersed in its mother liquor isa highly alkaline mixture. It is preferred to add the faujasite-motherliquor mixture to an acidic sodium silicate solution having a pH in thelower range, say from about 2.5 to about 3.5, such that the final pH ofthe reaction mixture is in the aforesaid range of from about 4.0 toabout 4.5. The addition should be accomplished as rapidly as possible toavoid undue exposure of the faujasite to the more acidic conditions. Therate of addition is limited only by the efficiency with which thefaujasite-mother liquor mixture is dispersed in the acidic sodiumsilicate solution. Should the alkaline mixture be added too rapidly withinadequate mixing, localized concentrations may occur in the reactionmixture in excess of the desired pH range. This has an adverse effect onthe homogeneity of the reaction mixture and ultimately on the uniformityof the final catalyst composite. By an alternative method, the acidicsodium silicate solution may be prepared with an initial pH, say fromabout 3.5 to about 4.5, and the pH controlled so as not to exceed about4.5 by adding a suitable acid separately but concurrently with thealkaline faujasite-mother liquor addition.

The acidified alkali metal silicate hereinabove referred to is availableby conventional methods of preparation. The alkali metal silicate mostoften employed is an aqueous sodium silicate solution commerciallyavailable as water glass. Acidification with a small amount of acid suchas hydrochloric acid, sulfuric acid, and the like, effects hydrolysis ofthe water glass and conversion thereof to a silicic acid or a silicasol. The water glass is usually diluted with water and added to the acidin the diluted state, the final pH being at least about 2.5 and not inexcess of 4.5. To obviate polymerization and premature gelation thereof,the temperature is maintained below about 100 F.

After a suitable period of time has elapsed during which the reactionmixture is permitted to age at the acidic conditions, preferably underconditions of rapid and continuous stirring, whereby the silica ispolymerized to a complex polysilicic acid, the slurry is adjusted to apH of from about 5 to about 8, preferably a pH of from about 6 to about7. The reaction mixture is thereafter aged for a time sufficient todevelop optimum pore structure of the silica hydrogel, a period of fromabout 0.5 to about 3 hours being suitable, a period of from about 0.5 toabout 1.5 hours being preferred.

The aged product is thereafter separated from the reaction mixture andbase-exchanged in contact with a solution containing an ion capable ofreplacing alkali metal ions, suitably an ammonium salt solution, andcharacterized by a pH in excess of about 4.5, so that the final catalystcomposite comprises less than about 1.0 weight percent alkali metal. Oneconvenient and preferred method comprises recovering the product as afilter cake. The filter cake is then reslurried or mixed with water to asmooth consistency and subjected to spray drying whereby the aqueousslurry is sprayed in an atomized state into an atmosphere of hot inertgases to efiect a rapid evaporation of moisture so that dried particlesof a predetermined size range fall out of the spray. If so desired, theaforesaid filter cake can be water-washed to concentrate and partiallyremove soluble salts prior to the spray drying process. Alternatively,the spray dried material can be reslurried and subjected to one or morewater-washings to reduce the soluble content to an acceptable level. Inany case, the aged hydrogel separated from the aforesaid reactionmixture is treated, preferably with an ammonium salt solution, to removesubstantially all of the sodium or other alkali metal ions, and thislast mentioned step may be combined with either or both of theaforementioned water-washing steps or may be separate and aparttherefrom.

The catalyst composite prepared in accordance with the process of thisinvention may be composited with any of the several catalytically activemetallic materials in the oxidized or reduced state. Of particularinterest are the rare earth metals, e.g., cerium, lanthanum,praseodyium, neodymium, illinium, Samarium, europium gadolinium,terbium, dysprosium, holmiurn, erbium, thulium, scandium, yttrium,lutecium, which are composited with the catalyst by base-exchangemethods in the ionic form together with hydrogen ions. Thus, thecatalyst composite of this invention can be further treated in contactwith an aqueous solution comprising both rare earth cations and hydrogenions, or hydrogen ion precursors such as ammonium ions. Organic andinorganic acids are generally considered as a convenient source ofhydrogen ions. However, it is preferred to utilize a hydrogen ionprecursor, particularly an ammonium salt such as ammonium chloride,which is decomposable to provide hydrogen ions at a temperature belowthe decomposition temperature of the faujasite. Anions introduced to thecomposite as a consequence of the base-exchange treatment are suitablyseparated by water-washing one or more times until free of said ions.The composite is thereafter dried generally in an air atmosphere, at anelevated temperature, a temperature of from about F. to about 600 F.beingsuitable. Catalysts thus prepared are particularly effective in thecracking of hydrocarbon feed stocks, such as occur in the gas-oil rangeof petroleum hydrocarbons, to form lower boiling hydrocarbons in themotor fuel range. Catalytic cracking conditions generally described inthe art apply. In particular, a temperature of from about 700 F. toabout 1200 F. may be employed and the pressure may range fromsubatmospheric to several atmospheres. The cracking process can beeifected by any of the well-known techniques including a fixed bed typeof operation, a moving bed type of operation and, in particular, thewell-known fluidized bed type of operation.

Also of interest are those catalysts comprising one or more metals ofGroup VI-B and VIII including molybdenum, tungsten, chromium, iron,nickel, cobalt, platinum, palladium, ruthenium, rhodium, osmium andiridium. Thus, the catalyst composite prepared in accordance with theprocess of this invention can be utilized advantageously as a catalystor component thereof to effect a variety of hydrocarbon conversionreactions involving reaction conditions comprising a temperature in the70- 1400 F. range. The catalyst composite of this invention isparticularly useful in combination with a hydrogenation component suchas nickel together with molybdenum, tungsten, etc. in effecting thehydrocracking of heavy oils, including vacuum residuals, in the presenceof hydrogen to form petroleum products in the middle distillate rangeutilizing a temperature of from about 500 F. to about 1000 F. andpressures of from about 500 p.s.i.g. to about 2500 p.s.i.g. Saidhydrocarbon conversion reactions further include polymerization ofolefins, particularly ethylene, propylene, l-butene, Z-butene,iso-butylene, and also higher boiling olefins, at polymerizationreaction conditions. The catalyst composite is also useful as a catalystor a component thereof in effecting the alkylation of isoparafiins witholefins or other alkalating agents including, for example, alkyl halidesand the like; and also for the alkylation of isobutane, isopentaneand/or isohexane with ethylene, propylene, l-butent, etc., or mixturesthereof; and also the alkylation of aromatics with olefins or otheralkylation agents, particularly the alkylation of benzene, toluene,etc., with propylene, and higher boiling olefins including nonenes,decenes, undecenes, etc., the foregoing alkylation reactions beingeffected at alkylation conditions disclosed in the art. The products ofthe process of this invention are further helpful in the isomerizationof parafiins, particularly n-butane, n-pentane, n-hexane, nheptane,n-octane, etc., and also the isomerization of less highly branched chainsaturated hydrocarbons such as the isomerization of 2- or3-methylpentane to 2,3- and 2,2-dimethylbutane, isomerization ofdirnethylcyclohexane to methylcyclohexane, isomerization ofmethylcyclopentane to cyclohexane, etc., at isomerization reactionconditions. Other hydrocarbon conversion reactions including hydrogentransfer reactions, transalkylation reactions, and the reforming ofgasoline or naphtha to improve the antiknock characteristics thereof,are effectively catalyzed utilizing the catalyst composite prepared inaccordance with this method as a catalyst or component thereof.

The following example is presented in illustration of one preferredembodiment of this invention and is not intended as an undue limitationon the generally broad scope of the invention as set out in the appendedclaims.

In the preparation of the faujasite dispersed in its mother liquor, 49.9pounds of sodium aluminate was dissolved in 215 pounds of a 30 weightpercent sodium hydroxide solution at about 140 F. The sodium aluminatecontained 31.0 weight percent Na O and 46.0 weight percent Al O and thesodium hydroxide solution contained 28.7 Weight percent Na O. Theresulting solution was cooled to about 100 F. and added to a rapidlystirred slurry, said slurry being an aqueous colloidal solution 159pounds) containing 96.0 weight percent SiO slurried in 472.6 pounds oftreated water. This reaction mixture was stirred at about 100 F. forabout 19 hours and then at about 203 F. for an additional hour.Thereafter, the reaction mixture was heated at about 203 F. withoutstirring for an additional 48 hours and then cooled to about 100 F.

An acidic sodium silicate solution was prepared by the addition of awater glass solution, containing 6.9 weight percent SiO and a SiO /Na Omolar ratio of 3.22, to a 25% sulfuric acid solution, the final pH beingabout 3 at 95 F. The resulting solution was stirred vigorously andsufiicient amount of the faujasite-mother liquor added to yield aboutweight percent faujasite in the finished catalyst. The final pH wasabout 4.2-4.4. Within about minutes gelation occurred and the stirringwas continued for an additional 30 minutes. The pH was then adjusted to6.0 by the addition of a 15 weight percent aqueous ammonia solution.After one hour aging at said pH the solids were separated from thesupernatant liquid, reslurried in water and spray dried. The spray driedproduct was thereafter washed with a dilute aqueous ammonium chloridesolution.

The resulting faujasite dispersed in an amorphous silica matrix wasfurther base-exchanged with a solution comprising ammonium chloride andmixed rare earth chlorides (57.92% rare earth chloride hexahydrate). Thebase-exchange was accomplished over a 2 hour period whereby the catalystcomposite contained about 1.5 weight percent rare earth metals. Thecatalyst composite was thereafter water-washed substantially free ofchloride and dried at 400 F. The catalyst thus prepared was steamdeactivated in preparation for testing as hereinafter described bypassing 60% steam in air in contact with the catalyst at a temperatureof 1400 F. for a period of 12 hours. The test consisted in passing a gasoil boiling in the range of 530-995 F. in contact with the catalyst atsubstantially atmospheric pressure at a feed rate of 4 weight hourlyspace velocity. Initial tests were run at a temperature of 930 F. todetermine conversion of the gas oil to gasoline having an end point of410 F. Thereafter, the temperature was adjusted as required to give a57% conversion. Each test consisted of 5 cycles and each cycle consistedof a processing period, a steam stripping period and an air regenerationperiod. The test results are tabulated below.

F. (required for 57% conversion) 896 Gasoline, weight percent 40.8Carbon, weight percent 4.7

I claim as my invention:

1. A process for manufacturing a catalytic composite of a faujasitedispersed in a silica matrix which comprises:

(a) preparing a faujasite dispersed in its mother liqour (b) rapidlydispersing the faujasite-mother liquor mixture in an acidified alkalimetal silicate solution having a pH in excess of about 2.5, controllingthe pH during the faujasite-mother liquor addition so as not to exceedabout 4.5, the final pH of the mixture in from about 4.0 to about 4.5,and effecting gelation of the mixture.

(0) adjusting the pH of the resulting slurry to a pH of from about 5 toabout 8 and aging the slurry for at least about 0.5 hour,

(d)-separating and base-exchanging the resulting solution in contactwith a solution containing ions capable of replacing alkali metal ionsand characterized by a pH in excess of about 4.5,

(e) washing the base-exchanged product free of soluble matter and dryingthe resultant catalytic composite.

2. The process of claim 1 further characterized with respect to step (a)in that said faujasite is prepared dis persed in its mother liquor byforming a sodium-aluminasilica-water mixture whose composition expressedin terms of oxide mole ratios falls in the range SiO /Al O from 6 to 20Na O/SiO from 0.3 to 0.7 H O/Na O from 25 to 60 maintaining the mixtureat a temperature of from about F. to about 245 F. and forming saidfaujasite dispersed in its mother liquor.

3. The process of claim 2 further characterized with respect to step (b)in that said faujasite-mother liquor mixture is dispersed in anacidified alkali metal silicate solution having a pH in excess of about2.5 and less than about 3.5, the pH being controlled during thefaujasitemother liquor addition so as not to exceed about 4.5, the finalpH of the mixture being from about 4.0 to about 4.5.

4. The process of claim 3 further characterized with respect to step (b)in that said gelation is elfected at a temperature of from about F. toabout F.

5. The process of claim 4 further characterized with respect to step (c)in that said slurry is adjusted to a pH of from about 6 to about 7 andaged for a period of from about 0.5 to about 1.5 hours.

6. The process of claim 5 further characterized with respect to step (d)in that said product is base-exchanged with said solution whereby thealkali metal content is reduced to less than about 1 weight percent ofsaid product.

References Cited UNITED STATES PATENTS 3,207,701 9/1965 Curtin 2524513,275,571 9/1966 Mattox 252451 3,329,627 7/1967 Gladrow et al. 252455 X3,352,796 11/1967 Kimberlin et al. 252-455 DANIEL E. WYMAN, PrimaryExaminer C. F. DEES, Assistant Examiner US. Cl. X.R. 252455

